All labelling on cold remedies changed in the last year or so. Even those specifically formulated for children. There was recently some research concluding that many not effective in young children AND many parents were re-dosing children when they didn't see any improvement or combining products without paying attention to those which had the same ingredients. There were children in the ER with overdoses.
For a child of six, you shouldn't use anything not labelled for her age unless your doctor directs you to do so.
If she has multiple ear infections in a year, it is time to see an ENT for treatment whether it be by medication or surgery.
My daughter is on her second set of tubes, but hers have a tendency to clog so we still have the occasional ear infection. I find the best way to head off a full blown infection is to start a several day treatment of Mucinex at the first signs of any congestion and make sure she is getting plenty of clear fluids. I also use saline up her nose a couple times a day to help everything blow up easier. A dose of Benadryl at night helps reduce post-nasal drip and acts to reduce any swelling of the sinuses. Both of those products are labelled for a child of six...I had to agree on doses with my doctor since my daughter is only three.
Nasal decongestants are good at reducing the swelling and drying up secretions, but a lot of mucus is produced in inner ear infections. Drying the mucus membranes may make things worse. Better to stimulate production and move them out of the area.
I tried a lot of natural remedies before my daughter got her first set of tubes. I found that an immunity boosting children's supplement seemed to help, as did reducing her intake of milk (especially when she starts to get congested).
Good Luck!